The present invention relates to fasteners, particularly to male fastener components for hook and loop fasteners, to methods of manufacturing them, and to their use in securing a mesh material to a window frame to provide a temporary insect screen.
It is common, particularly in the United States, to provide windows with permanent screens to allow the windows to be opened without admitting insects. However, such screens are not always provided, and in fact are relatively uncommon in homes in Europe. To meet the need for screening in these situations, temporary screens have been developed. These screens are generally installed when insects are present and removed when insects are not present, by removably attaching a sheet of mesh material to an attachment strip that is adhered to the window frame. Generally these temporary screens are mounted on the inside of the window.
Attachments strips have been formed of, among other things, the male component of a hook and loop type fastener. To secure the screen, the male fastener elements are inserted through the openings of the mesh material and engage the sides of the mesh openings. It is desirable that the engagement between the male fastener elements and the mesh openings provide good peel strength, so that the screen is not detached by wind, and that the attachment strip be inexpensive and relatively attractive.
There is also a general need for male fastener components for hook and loop fasteners that provide good multidirectional peel and shear strength properties and that are relatively inexpensive to manufacture.
In one aspect, the present invention features a method of forming a fastener. The method includes: (a) forming, from a thermoformable material, a preform product having a sheet-form base and an array of preform stems integrally molded with and extending from the base to corresponding terminal ends; (b) heating the terminal ends of the stems to a predetermined softening temperature, while maintaining the sheet-form base and a lower portion of each stem at a temperature lower than the softening temperature; and (c) contacting the terminal ends with a contact surface that is at a predetermined forming temperature, to deform the terminal ends to form heads therefrom that overhang the sheet-form base.
Preferred methods include one or more of the following features. The forming temperature is sufficiently low that the thermoformable material does not adhere to the contact surface. The forming temperature is lower than the softening temperature. The contact surface comprises the cylindrical surface of a roll. The contact surface is cooled to maintain the forming temperature during step (c). In step (c), the heads that are formed are substantially disc-shaped or mushroom-shaped. The thickness of each disc-shaped head is from about 5 to 15% of the equivalent diameter of the disc. The head has a substantially dome-shaped surface overhanging the base. Step (a) includes molding the stems in molding cavities in a mold roll. In step (b), the region extends from the terminal end towards the base a distance equal to from about 15 to 25% of the total distance from the terminal end to the base. The contact surface has a surface finish selected from the group consisting of dimpled, smooth, textured, and combinations thereof. The surface finish comprises dimples and the contact surface includes a density of dimples per unit area of the contact surface that is greater than or equal to the density of stems per unit area of the base. During step (c), the dimples are in at least partial registration with the stems.
In another aspect, the invention relates to a method of forming a fastener, including: (a) forming a plurality of stems, extending from a common base to a terminal end, from a thermoformable material; (b) heating a region of the stems adjacent the terminal ends to a predetermined softening temperature, to soften the material in the region, while maintaining the remaining portion of the stems at a temperature lower than the softening temperature; and (c) contacting the terminal ends with a contact surface to form heads at the terminal end of the stems, at least a portion of the contact surface having a sufficiently rough texture to impart a loop-engaging surface roughness to at least a portion of the heads.
Preferred methods include one or more of the following features. The contact surface comprises the cylindrical surface of a roll. The contact surface has a sandpaper-like texture. The contact surface has a surface roughness (rugosity) of about 10 to 200 microns. The contact surface defines a plurality of dimples. The contact surface includes a density of dimples per unit area of the contact surface that is greater than or equal to the density of stems per unit area of the base. The surface roughness imparted to the heads is sufficient to increase the peel strength of the fastener by from about 10 to 100%.
In yet another aspect, the invention features a fastener element including an elongated stem extending and molded integrally with a substantially planar base, and a head disposed at a terminal end of the stem, at least a portion of the head having a rough surface having a sandpaper-like surface texture.
Preferred fastener elements include one or more of the following features. The rough surface has a surface roughness (rugosity) of from about 10 to 200 microns. The rough surface has sufficient surface roughness to increase the peel strength of the fastener by from 10 to 100%. The head is substantially disc-shaped or mushroom-shaped.
The invention also features an attachment strip for attaching a mesh screen to a surface. The attachment strip includes (a) a substantially planar base; (b) a plurality of elongated stems extending from the base; and (c) a plurality of heads, each head being disposed at a terminal end of one of the stems. According to one aspect of the invention, at least a portion of the heads have a rough surface having a sandpaper-like surface texture.
The term xe2x80x9cdisc-shapedxe2x80x9d, as used herein, refers to a shape having top and bottom surfaces, at least a portion of the top surface being substantially parallel to a corresponding portion of the bottom surface, and having a thickness that is substantially less than its equivalent diameter. xe2x80x9cEquivalent diameterxe2x80x9d means (a) for a circular disc, the actual diameter, and (b) for a disc having a non-circular shape, the diameter of a circular disc having the same thickness and surface area as the non-circular disc. When viewed from above, the disc-shape may be substantially circular, irregular in shape but approximately circular, or non-circular, e.g., square or cross-shaped. The disc-shape may be flat, or may have other shapes such as domed, wavy, or pyramidal.
The term xe2x80x9cmushroom-shapedxe2x80x9d, as used herein, refers to any shape having a domed portion, with the exception of a complete sphere.
The phrase xe2x80x9cloop-engaging surface roughnessxe2x80x9d, as used herein, means a degree of surface roughness that is sufficient to xe2x80x9ccatchxe2x80x9d on a loop fastener element and provide a partial, momentary engagement therewith.
The term xe2x80x9csandpaper-likexe2x80x9d, as used herein, means a surface roughness akin to the surface texture of sandpaper.
The fastener elements of the invention have a head geometry that advantageously provides a strong attachment to a female fastener component. The fastener elements are particularly well adapted for use in fastener tapes for attaching an insect screen to a window frame, as the head geometry provides a strong engagement with the mesh of the insect screen. Insect screen fastener tapes of the invention exhibit good peel strength and thus good resistance to detachment due to wind. The methods of the invention allow the fastener elements to be manufactured using a relatively simple and economical process.
Other features and advantages will become apparent from the following Description of the Preferred Embodiments, the drawings and the claims.